Well, you can probably figure a normal fight runs four to six turns, and a big fight or boss battle might run twice that long. So multiply by the number of fights in the modules and the number of shots per turn, and you should be able to approximate it from there.

But there isn't a fixed number of fights in those modules. It depends on how your skills roll out, how long you take, what you choose to do, and a lot of other things. I don't think it's possible to even vaguely approximate how many combat-rounds there might be across both modules because it just really depends.